Pneumatic circuit



PNEUMATI C CIRCUIT Filed Nov. 30, 1965 IN VENTOR Alessandro 'fi ATTORNEY United States Patent 3,375,843 PNEUMATIC CIRCUIT Alessandro Buratti, Bari, Italy, assignor to Pignone Sud S.p.A., Bari, Italy, a company of Italy Filed Nov. 30, 1965, Ser. No. 510,594 Claims priority, application Italy, Jan. 14, 1965, 251, Patent 748,715 1 Claim. (Cl. 137-85) ABSTRACT OF THE DISCLOSURE Flow of fluid to a nozzle is maintained by providing two restrictions in the supply duct. Supply is connected to the duct which, in turn is, connected to a supply chamber. Between its first and second restrictions the duct is connected to an output chamber from which the fluid can flow to an exhaust duct. Between the second restriction and the nozzle, the duct is connected to a signal chamber. Two flexible partitions separate the signal chamber from a discharge chamber, and the discharge and output chambers, respectively. A port in the second-mentioned partition connects discharge and output chambers. A second port connects supply and output chambers. A twoheaded valve is normally spring pressed to close both ports.

The present invention relates to improvements in pneumatic measurement, transmission, adjustment and control systems, that is, transmission systems, positioning devices, governing devices, electro-pneumatic transducers and the like.

More particularly, this invention relates to a particular circuit arrangement of a few component parts which are common to all the above listed devices.

The principal object of the present invention is to make the devices more accurate, more responsive, more stable, that is, to make their output pressure less dependent upon foreign factors and especially variations of the supply pressure, more closely related in a linear relationship with the input signal, faster in following the input signal.

The patents: U.K. 806,749 of Nov. 28, 1955, Germany No. 1,074,899 of June 19, 1956 and Italy No. 621,819 based on the Czechoslovakian Patent No. 96,655-6 'of Feb. 15, 1958 represent an improvement over the conventional circuit arrangement of the system: restrictionnozzle-flapper-amplifying relay, consisting in feeding the restriction with the fluid coming out of the relay instead of the supply fluid.

The present invention represents a further improvement over the arrangement cited above and precisely (see FIG. 1 wherein a=supply; w=output) it consists of: a restriction 1 fed by the supply fluid; a second restriction 2 downstream the former one; a nozzle 3 downstream of two restrictions 1 and 2; a flapper 4 for said nozzle 3 actuated by a movable part of the device, not shown in the drawing; an amplifying relay 5 comprising a supply chamber 6, an output chamber 7, a discharge chamber 8, a signal chamber 9, a double acting plug 10, a movable body 11 and a biasing spring 12.

The conduit 13 between the two restrictions is in communication with the output chamber, whereas the conduit 14 between restriction 2 and nozzle 3 is in communication with the signal chamber.

Restrictions 1 and 2 are proportioned, relatively to the supply, output and signal pressures, so that, in steady flow conditions, the rate of flow through restriction 1 is al ways greater than the rate of flow through restriction 2.

The excess flow is sent to the output chamber 7 and, when the device is balanced, and no fluid is taken at the output, it is discharged into discharge chamber 8 through discharge port 15. Thus the movable body 11 is set apart from plug 10. Thus avariation of the force applied to the plug, due to a variation of the supply pressure, does not have any influence on the movable body 11 and thus also on the output pressure. Conversely, in the arrangements according to the above cited patents, the plug is continually pressed by the movable body in. order to keep the output port closed and the intake port slightly open; only thus a continuous flow of fluid may reach the nozzle.

Consequently, a variation of the force applied to the plug, due to a variation of the supply pressure, is directly transmitted to the movable body and, for balance involves variations of the output pressure.

The spring 12, which is very weak, has only the function of keeping the movable body resting on the plug at start up, and thus, with the whole system at atmosphere pressure, so that, when fed, the system can enter steady flow conditions.

I claim:

1. A pneumatic relay of the type having a housing defining an inlet chamber, an outlet chamber, a discharge chamber and a signal pressure chamber, movable pressure responsive wall means defining said discharge chamber and one wall of said outlet chamber and signal pressure chamber respectively, valve means for connecting said inlet and outlet chambers responsive to one direction of movement of said movable wall means and for connecting said outlet and discharge chambers responsive to movement of said movable wall means opposite said one direction, a source of fluid under pressure connected to said inlet chamber, a nozzle, a flapper operatively associated with the nozzle for varying the nozzle opening, and conduit means connecting the source of fluid with the nozzle inlet; the improvement comprising: a first restriction in said conduit means located between said inlet chamber and said nozzle, a second restriction of smaller flow capacity than the first restriction in said conduit means in series with the first restriction and located between the first restriction and the nozzle, means unrestrictedly connecting the conduit means at a location between the restrictions with the outlet chamber, and means unrestrictedly connecting the conduit means at a location between the second restriction and the nozzle with the signal pressure chamber.

ALAN COHAN, Primary Examiner. 

